Froth flotation is a process used to selectively separate hydrophobic from hydrophilic materials. While applicable in a number of industries, one area of great importance is the mining industry where it is commonly used for the recovery of metal sulfide ores or coal, for example. The key steps in the process involve initially grinding the ore (a process known as ‘comminution’) to a relatively fine particle size in order to ‘liberate’ the valuable mineral from the remaining commercially worthless material (known as ‘gangue’). Following this step, the ground ore is mixed with water to form a ‘slurry’ and a surfactant (or ‘collector’) is commonly added to bind to the surface of the desired mineral to render it hydrophobic. The slurry is introduced into an aerated flotation cell (often mechanically agitated with an impeller) such that the hydrophobic particles collide and bind with the air bubbles and rise to the surface of the cell, forming a froth of purified mineral which is then collected.
Industrial processes such as fluid mixing and solid particulate transport, as discussed above with respect to froth flotation, involve a multi-phase flow that is often pumped through complex geometry or mixed using an impeller. Due to the large scale of some mixing and transport processes, the flow will be turbulent and traveling at a high velocity. Improvements to such processes can potentially yield significant savings in energy and/or other costs. An understanding of the fluid dynamics may facilitate the ability to aid design and optimization of fluid mixing/transport processes.
Techniques for gaining insight into the details of a fluid flow come from the fields of Computational Fluid Dynamics (CFD) and Experimental Fluid Dynamics (EFD). Due to limitations associated with predicting complicated flow regimes, an EFD approach is often taken. Available EFD technologies include Laser Doppler Anemometry (LDA), Particle Image Velocimetry (PIV), Hot Film Anemometry (HFA), Ultrasound Velocity Profiler (UVP) and piezoelectric force sensors. The majority of these techniques rely on the working fluid being transparent such that light is able to penetrate the fluid. Some industrial processes, however, involve opaque liquid-solid mixtures such as slurries and/or opaque containers. Techniques that require transparency are impractical under such conditions.